It's a lot more than $50 now, unless you can scrounge some of the materials for free, but it does work in a lot of areas. I built a similar one, only shorter.
Today, though, we are expecting golf-ball sized hail and 60+ mph winds in Central Iowa. If you live in an area with this sort of weather, you might want to either use a different design or have wagons and an alternative place to move your plants before the storm(s).
For the record, my warm season flowers and veggie starts are still inside, on the kitchen table.